Promotion of foreign gene expression is the most required technique in applying the genetic engineering technique to plants. One of the techniques is the utilization of DNA fragments. Known DNA fragments which promote expression of foreign genes include some introns (Simpson and Filipowicz 1996. Plant Mol. Biol. 32: 1–41) including an intron of maize alcohol dehydrogenase (Callis et al. Gene & Development 1, 1183–1200 (1987)), as well as the first intron of rice phospholipase D (WO96/30510). Influences of deletion of apart of inner regions of DNA fragments derived from introns, and of insertion of the same intron into the intron, on the promotion of expression have been reported (Mascarenhas et al. Plant Mol. Biol. 15, 913–920 (1990), Clancy et al. Plant Sci. 98, 151–161 (1994)).
However, so far, types of available DNA fragments are limited. Further, actions of the DNA fragments vary depending on the type of the plant, and vary depending on the organs or tissues even in the same plant (Simpson and Filipowicz 1996. Plant Mol. Biol. 32: 1–41). Therefore, existence of DNA fragments exhibiting various types of expression-promotion actions is desired.